Reference is made to patent application Ser. No. 535,496, now abandoned, entitled "Apparatus For Operating a Fluorescent Lamp" the contents of which are incorporated herein by reference as additional background information.
Almost all commercial and industrial facilities utilize fluorescent lighting. Compared to an incandescent lamp, a fluorescent offers a far greater degree of efficiency. For an equivalent power rating, a fluorescent tube will develop five to six times the luminosity. Moreover, even using conventional heated filament starting circuits, the lifetime of a typical fluorescent lamp is approximately eight times that of an incandescent bulb.
A fluorescent lamp is an electric discharge light source. It consists of a phosphor coated glass tube with a cathode sealed in each end. Before the tube is sealed, the air is exhausted from it. Then small quantities of an inert gas mixture and a small amount of mercury are introduced. When the mercury is ionized as the result of an electrical potential ultra-violet radiation is produced. The ultra-violet radiation causes the phosphor coated walls to emit light.
Although there are a number of different types of fluorescent lamps and operating circuits, most commercial and industrial lighting systems in the United States employ a transformer type ballast which preheats the filament to facilitate starting. Accordingly, the advantages of the present invention will be described by comparison with such systems which are commonly referred to as rapid start types.
In a typical rapid start installation, a number of ballast transformers are connected in parallel across a single electrical circuit. Each ballast transformer operates one of two fluorescent tubes (depending upon the transformer design). The standard ballast transformer comprises a pair of windings for heating the filament and a "step up" secondary which is purposely designed to have a large leakage inductance. It serves the multiple function of, (1) raising the voltage to strike the arc, and (2) limiting the lamp operating current after ignition takes place (the large leakage inductance being equivalent to a series choke once the lamp is started), and (3) heating the filaments to aid in starting. These ballast have several disadvantages, namely:
1. Ballast transformers are heavy and relatively expensive in terms of the other components (e.g., the fluorescent tubes and fixtures).
2. Leak transformers are inefficient --approx. 20% of the applied power is lost in the form of heat which must be removed by the buildings'air conditioning system.
3. Although the filament windings are only used to facilitate starting, power is continuously applied to these elements as long as the lamp is operated--thus producing an additional heat loss.
As previously stated, fluorescent lamps are considerably more efficient than incandescent bulbs. Yet because of the tremendous number of such bulbs in commercial and industrial use, the total power consumption attributable to such lights is a relatively high percentage of the overall electrical energy consumption.* In view of the fact that the projected demands for electrical energy exceed the nation's ability to produce this form of power, the importance of increased commercial and industrial lighting efficiency will be readily appreciated. FNT According to a three volumn Rand Study entitled "California Electricity Quandary" commercial lighting may consume as much as 37% of the state's electricity.
Accordingly, a primary object of the present invention is to provide a more efficient system for operating fluorescent lamps.
A further object of the present invention is to provide a fluorescent lighting system which does not require a transformer to step-up the voltage.
Another object of the invention is to provide a starting arrangement which does not utilize continuously heated filaments.
Another object of the present invention is to provide a non-inductive ballast system for operating a plurality of fluorescent lamps from a single source.
An additional object of the present invention is to provide novel means for starting fluorescent lamps which does not employ conventional step-up transformers or inductive kick ballasts.
Other objects and advantages of the present invention will be obvious from the detailed description of a preferred embodiment given herein below.